Alkaline storage batteries which use a negative electrode including a hydrogen storage alloy as a negative electrode active material, has high output characteristics as well as high durability (in terms of, for example, life characteristics and/or storage characteristics). Therefore, attention is being focused on such alkaline storage batteries as, for example, alternatives for dry-cell batteries and a power source for, for example, electric vehicles. However, in recent years, lithium-ion secondary batteries have also been used for such purposes. Therefore, in view of emphasizing the advantages of alkaline storage batteries, battery characteristics such as output characteristics and durability are expected to be further improved.
For the hydrogen storage alloy, a hydrogen storage alloy having a CaCu5-type crystal structure has been primarily used. When a high alloy capacity is required, a hydrogen storage alloy including a Ce2Ni7-type or CeNi3-type crystal structure has been used. To improve battery characteristics of alkaline storage batteries, attempts have been made to optimize the abilities of the hydrogen storage alloy in powder form.
For example, Patent Literature 1 proposes using a hydrogen storage alloy including an element A such as La or Mg and an element B such as Co or Ni, in a negative electrode for an alkaline secondary battery. For the element B, Ge, Sn, and other elements are also given as examples.
Patent Literature 2 proposes adding an oxide or hydroxide of Ge to a negative electrode for a nickel-metal hydride battery which uses a hydrogen storage alloy, such that the amount of Ge in the hydrogen storage alloy falls in the range of 0.01 to 2 weight %.
Patent Literature 3 discloses an alkaline secondary battery in which a negative electrode includes as a main component a Mg—Ni alloy including an amorphous phase capable of absorbing and releasing hydrogen, the Mg—Ni alloy surface covered with a layer of an insulating material including a hydrate or hydroxide including Mg and, for example, Ge.